Adsorption Properties and Mechanism of Biochar Aging on Cd2+in Soil
Aging of biochar can affect its stability and persistence of heavy metals immobilizing in soil,resulting in changes in its inertness.Using peanut shell(PS)as raw material,peanut shell biochar(PSB)was prepared by pyrolysis under the condition of 600 ℃ and hypoxia.Oxidized biochar(OPSB),leached biochar(LPSB)and acidified biochar(APSB)were prepared Y by simulated field oxidation,leaching and acidification of PSB.The effects of these three aging methods on the adsorption efficiency and mechanisms of Cd2+by the biochar were investigated using isothermal adsorption models,kinetic models,FT-IR and XRD.The results show that oxidative aging process an significantly enhance the accumulation of oxygen-containing functional groups(—COOH,—OH,etc.)on the surface of the biochar,thereby increasing the adsorption capacity of OPSB for Cd2+by 10.13％.Leaching aging process can not cause significant changes in functional group content but result in substantial loss of soluble minerals,leading to a significant decrease adsorption capacity of LPSB for Cd2+by 13.35％.Acidification aging process can affect the adsorptive activity of Cd2+on the surface of the biochar,resulting in a reduction in adsorption capacity of APSB for Cd2+by 26.52％.All four types of biochar exhibite effective adsorption for Cd2+,the OPSB showing optimal affinity followed by PSB,LPSB,and APSB.The Langmuir isothermal adsorption model provides better fitting for describing the Cd2+adsorption process by all four types of biochars under low pH conditions.Furthermore,the adsorptions processes by all four types of biochars are predominantly governed by physical electrostatic interactions,which is suitable to be described by quasi-first-order kinetic model.
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